Biodegradable polyester is a kind of macromolecule material using biological resources as raw materials. With respect to a petroleum-based polymer using petrochemical resources as raw materials, the biodegradable polyester can be degraded during a process of biological or biochemical effect or in a biological environment, being a very active degradable material in the present biodegradable plastic research and one of the best degradable materials in market application.
The biodegradable polyester of which substrate is aliphatic-aromatic polyester and polylactic acid, usually causes phenomenons such as broken holes and white stripes, on a surface of film material during film blow molding, which affects a surface appearance property of film material, owing to a relatively poor compatibility between aliphatic-aromatic polyester and polylactic acid. In order to improve the compatibility of those two, a conventional method is to add a copolymer which contains epoxy group and is based on styrene, acrylate and/or methacrylate, or to add a chain extender such as diisocyanate (CN103687902A, CN 102712766 B). Addition of a suitable amount of the chain extender improves the compatibility between aliphatic-aromatic polyester and polylactic acid to great extent and optimizes a surface property of film material. However, owing to fluctuations of factors such as an additive amount of the chain extender and a processing temperature, a chain extension reaction will tend to cause phenomenons such as insufficient chain extension or excessive chain extension, resulting in a plastic point (a fisheye) which is difficult to be plasticized on the surface of film material. This brings up a high demand on a modification technology and a processing technology and is difficult to satisfy a continuous production in large scale.
The present invention surprisingly finds by research that by adding a trace amount of glycidyl methacrylate into a chosen formula of the biodegradable polyester composition and controlling a weight content of glycidyl methacrylate which finally remains in the biodegradable polyester composition as 0.05 ppm-10 ppm, the compatibility between aliphatic-aromatic polyester and polylactic acid in the biodegradable polyester composition can be greatly enhanced, which enables the biodegradable polyester composition to have excellent surface property of film material, and no fisheye occurs on the film material because of the fluctuation of processing technique.